China brought in a one-child policy 25 years ago in a drive to curb population growth.

Urban couples are offered strong incentives to have no more than one child, while rural families are allowed up to two.

However, the government does not authorise health workers to carry out forced sterilisation and abortions.

China is the world's most populous country, with a population of more than 1.3 billion people.

'Detention'

China's National Population and Family Planning Commission said it had received "successive complaints" about illegal practices in Linyi.

"Some persons concerned in a few counties and townships of Linyi did commit practices that violated law and infringed upon legitimate rights and interests of citizens while conducting family planning work," a statement from the commission said.

It did not give any further details and there no explicit mention of abortion or sterilisation.

It is not known how many health officials were jailed or dismissed for their actions.

Chen Guangcheng, an activist who has championed the rights of couples that have complained of forced abortion or sterilisation, said he was detained for 30 hours this month by officials claiming to be police from Linyi.

He is quoted by the Reuters news agency as saying that the authorities had forced couples who had two children to undergo sterilisation, while women expecting a third child were forced to undergo abortions.